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nimbus-eth2/beacon_chain/consensus_object_pools/attestation_pool.nim
Etan Kissling 5dcfb0c4e7
avoid packing attestations from other forks (#3893) 
When there is heavy forking, proposals may get missed due to including
attestations from different forks that later fail verification.
Checking attestation signatures when building blocks should fix this.
2022-07-21 14:04:56 +03:00

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# beacon_chain
# Copyright (c) 2018-2022 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
{.push raises: [Defect].}
import
# Standard libraries
std/[tables, sequtils],
# Status libraries
metrics,
chronicles, stew/[byteutils, results],
# Internal
../spec/[
beaconstate, eth2_merkleization, forks, helpers,
state_transition_epoch, validator],
../spec/datatypes/[phase0, altair, bellatrix],
"."/[spec_cache, blockchain_dag, block_quarantine],
../fork_choice/fork_choice,
../beacon_clock
export tables, results, phase0, altair, bellatrix, blockchain_dag, fork_choice
const
ATTESTATION_LOOKBACK* =
min(24'u64, SLOTS_PER_EPOCH) + MIN_ATTESTATION_INCLUSION_DELAY
## The number of slots we'll keep track of in terms of "free" attestations
## that potentially could be added to a newly created block
type
OnAttestationCallback* = proc(data: Attestation) {.gcsafe, raises: [Defect].}
Validation* = object
## Validations collect a set of signatures for a distict attestation - in
## eth2, a single bit is used to keep track of which signatures have been
## added to the aggregate meaning that only non-overlapping aggregates may
## be further combined.
aggregation_bits*: CommitteeValidatorsBits
aggregate_signature*: AggregateSignature
AttestationEntry* = object
## Each entry holds the known signatures for a particular, distinct vote
data*: AttestationData
committee_len*: int
singles*: Table[int, CookedSig] ## \
## On the attestation subnets, only attestations with a single vote are
## allowed - these can be collected separately to top up aggregates with -
## here we collect them by mapping index in committee to a vote
aggregates*: seq[Validation]
AttestationTable* = Table[Eth2Digest, AttestationEntry]
## Depending on the world view of the various validators, they may have
## voted on different states - this map keeps track of each vote keyed by
## hash_tree_root(AttestationData)
AttestationPool* = object
## The attestation pool keeps track of all attestations that potentially
## could be added to a block during block production.
## These attestations also contribute to the fork choice, which combines
## "free" attestations with those found in past blocks - these votes
## are tracked separately in the fork choice.
candidates*: array[ATTESTATION_LOOKBACK, AttestationTable] ## \
## We keep one item per slot such that indexing matches slot number
## together with startingSlot
startingSlot*: Slot ## \
## Generally, we keep attestations only until a slot has been finalized -
## after that, they may no longer affect fork choice.
dag*: ChainDAGRef
quarantine*: ref Quarantine
forkChoice*: ForkChoice
nextAttestationEpoch*: seq[tuple[subnet: Epoch, aggregate: Epoch]] ## \
## sequence based on validator indices
onAttestationAdded*: OnAttestationCallback
logScope: topics = "attpool"
declareGauge attestation_pool_block_attestation_packing_time,
"Time it took to create list of attestations for block"
proc init*(T: type AttestationPool, dag: ChainDAGRef,
quarantine: ref Quarantine,
onAttestation: OnAttestationCallback = nil): T =
## Initialize an AttestationPool from the dag `headState`
## The `finalized_root` works around the finalized_checkpoint of the genesis block
## holding a zero_root.
let finalizedEpochRef = dag.getFinalizedEpochRef()
var forkChoice = ForkChoice.init(finalizedEpochRef, dag.finalizedHead.blck)
# Feed fork choice with unfinalized history - during startup, block pool only
# keeps track of a single history so we just need to follow it
doAssert dag.heads.len == 1, "Init only supports a single history"
var blocks: seq[BlockRef]
var cur = dag.head
# When the chain is finalizing, the votes between the head block and the
# finalized checkpoint should be enough for a stable fork choice - when the
# chain is not finalizing, we want to seed it with as many votes as possible
# since the whole history of each branch might be significant. It is however
# a game of diminishing returns, and we have to weigh it against the time
# it takes to replay that many blocks during startup and thus miss _new_
# votes.
const ForkChoiceHorizon = 256
while cur != dag.finalizedHead.blck:
blocks.add cur
cur = cur.parent
info "Initializing fork choice", unfinalized_blocks = blocks.len
var epochRef = finalizedEpochRef
for i in 0..<blocks.len:
let
blckRef = blocks[blocks.len - i - 1]
status =
if i < (blocks.len - ForkChoiceHorizon) and (i mod 1024 != 0):
# Fork choice needs to know about the full block tree back through the
# finalization point, but doesn't really need to have overly accurate
# justification and finalization points until we get close to head -
# nonetheless, we'll make sure to pass a fresh finalization point now
# and then to make sure the fork choice data structure doesn't grow
# too big - getting an EpochRef can be expensive.
forkChoice.backend.process_block(
blckRef.root, blckRef.parent.root, epochRef.checkpoints)
else:
epochRef = dag.getEpochRef(blckRef, blckRef.slot.epoch, false).expect(
"Getting an EpochRef should always work for non-finalized blocks")
let blck = dag.getForkedBlock(blckRef.bid).expect(
"Should be able to load initial fork choice blocks")
var unrealized: FinalityCheckpoints
if enableTestFeatures in dag.updateFlags and blckRef == dag.head:
unrealized = withState(dag.headState):
when stateFork >= BeaconStateFork.Altair:
state.data.compute_unrealized_finality()
else:
var cache: StateCache
state.data.compute_unrealized_finality(cache)
withBlck(blck):
forkChoice.process_block(
dag, epochRef, blckRef, unrealized, blck.message,
blckRef.slot.start_beacon_time)
doAssert status.isOk(), "Error in preloading the fork choice: " & $status.error
info "Fork choice initialized",
justified = shortLog(getStateField(
dag.headState, current_justified_checkpoint)),
finalized = shortLog(getStateField(dag.headState, finalized_checkpoint))
T(
dag: dag,
quarantine: quarantine,
forkChoice: forkChoice,
onAttestationAdded: onAttestation
)
proc addForkChoiceVotes(
pool: var AttestationPool, slot: Slot,
attesting_indices: openArray[ValidatorIndex], block_root: Eth2Digest,
wallTime: BeaconTime) =
# Add attestation votes to fork choice
if (let v = pool.forkChoice.on_attestation(
pool.dag, slot, block_root, attesting_indices, wallTime);
v.isErr):
# This indicates that the fork choice and the chain dag are out of sync -
# this is most likely the result of a bug, but we'll try to keep going -
# hopefully the fork choice will heal itself over time.
error "Couldn't add attestation to fork choice, bug?", err = v.error()
func candidateIdx(pool: AttestationPool, slot: Slot): Opt[int] =
if slot >= pool.startingSlot and
slot < (pool.startingSlot + pool.candidates.lenu64):
Opt.some(int(slot mod pool.candidates.lenu64))
else:
Opt.none(int)
proc updateCurrent(pool: var AttestationPool, wallSlot: Slot) =
if wallSlot + 1 < pool.candidates.lenu64:
return # Genesis
let
newStartingSlot = wallSlot + 1 - pool.candidates.lenu64
if newStartingSlot < pool.startingSlot:
error "Current slot older than attestation pool view, clock reset?",
startingSlot = pool.startingSlot, newStartingSlot, wallSlot
return
# As time passes we'll clear out any old attestations as they are no longer
# viable to be included in blocks
if newStartingSlot - pool.startingSlot >= pool.candidates.lenu64():
# In case many slots passed since the last update, avoid iterating over
# the same indices over and over
pool.candidates = default(type(pool.candidates))
else:
for i in pool.startingSlot..newStartingSlot:
pool.candidates[i.uint64 mod pool.candidates.lenu64] = AttestationTable()
pool.startingSlot = newStartingSlot
func oneIndex(bits: CommitteeValidatorsBits): Opt[int] =
# Find the index of the set bit, iff one bit is set
var res = Opt.none(int)
for idx in 0..<bits.len():
if bits[idx]:
if res.isNone():
res = Opt.some(idx)
else: # More than one bit set!
return Opt.none(int)
res
func toAttestation(entry: AttestationEntry, validation: Validation): Attestation =
Attestation(
aggregation_bits: validation.aggregation_bits,
data: entry.data,
signature: validation.aggregate_signature.finish().toValidatorSig()
)
func updateAggregates(entry: var AttestationEntry) =
# Upgrade the list of aggregates to ensure that there is at least one
# aggregate (assuming there are singles) and all aggregates have all
# singles incorporated
if entry.singles.len() == 0:
return
if entry.aggregates.len() == 0:
# If there are singles, we can create an aggregate from them that will
# represent our best knowledge about the current votes
for index_in_committee, signature in entry.singles:
if entry.aggregates.len() == 0:
# Create aggregate on first iteration..
entry.aggregates.add(
Validation(
aggregation_bits: CommitteeValidatorsBits.init(entry.committee_len),
aggregate_signature: AggregateSignature.init(signature)
))
else:
entry.aggregates[0].aggregate_signature.aggregate(signature)
entry.aggregates[0].aggregation_bits.setBit(index_in_committee)
else:
# There already exist aggregates - we'll try to top them up by adding
# singles to them - for example, it may happen that we're being asked to
# produce a block 4s after creating an aggregate and new information may
# have arrived by then.
# In theory, also aggregates could be combined but finding the best
# combination is hard, so we'll pragmatically use singles only here
var updated = false
for index_in_committee, signature in entry.singles:
for v in entry.aggregates.mitems():
if not v.aggregation_bits[index_in_committee]:
v.aggregation_bits.setBit(index_in_committee)
v.aggregate_signature.aggregate(signature)
updated = true
if updated:
# One or more aggregates were updated - time to remove the ones that are
# pure subsets of the others. This may lead to quadratic behaviour, but
# the number of aggregates for the entry is limited by the number of
# aggregators on the topic which is capped `is_aggregator` and
# TARGET_AGGREGATORS_PER_COMMITTEE
var i = 0
while i < entry.aggregates.len():
var j = 0
while j < entry.aggregates.len():
if i != j and entry.aggregates[i].aggregation_bits.isSubsetOf(
entry.aggregates[j].aggregation_bits):
entry.aggregates[i] = entry.aggregates[j]
entry.aggregates.del(j)
dec i # Rerun checks on the new `i` item
break
else:
inc j
inc i
func covers(entry: AttestationEntry, bits: CommitteeValidatorsBits): bool =
for i in 0..<entry.aggregates.len():
if bits.isSubsetOf(entry.aggregates[i].aggregation_bits):
return true
false
proc addAttestation(entry: var AttestationEntry,
attestation: Attestation,
signature: CookedSig): bool =
logScope:
attestation = shortLog(attestation)
let
singleIndex = oneIndex(attestation.aggregation_bits)
if singleIndex.isSome():
if singleIndex.get() in entry.singles:
trace "Attestation already seen",
singles = entry.singles.len(),
aggregates = entry.aggregates.len()
return false
debug "Attestation resolved",
singles = entry.singles.len(),
aggregates = entry.aggregates.len()
entry.singles[singleIndex.get()] = signature
else:
# More than one vote in this attestation
if entry.covers(attestation.aggregation_bits):
return false
# Since we're adding a new aggregate, we can now remove existing
# aggregates that don't add any new votes
entry.aggregates.keepItIf(
not it.aggregation_bits.isSubsetOf(attestation.aggregation_bits))
entry.aggregates.add(Validation(
aggregation_bits: attestation.aggregation_bits,
aggregate_signature: AggregateSignature.init(signature)))
debug "Aggregate resolved",
singles = entry.singles.len(),
aggregates = entry.aggregates.len()
true
proc addAttestation*(pool: var AttestationPool,
attestation: Attestation,
attesting_indices: openArray[ValidatorIndex],
signature: CookedSig,
wallTime: BeaconTime) =
## Add an attestation to the pool, assuming it's been validated already.
##
## Assuming the votes in the attestation have not already been seen, the
## attestation will be added to the fork choice and lazily added to a list of
## attestations for future aggregation and block production.
logScope:
attestation = shortLog(attestation)
doAssert attestation.signature == signature.toValidatorSig(),
"Deserialized signature must match the one in the attestation"
updateCurrent(pool, wallTime.slotOrZero)
let candidateIdx = pool.candidateIdx(attestation.data.slot)
if candidateIdx.isNone:
debug "Skipping old attestation for block production",
startingSlot = pool.startingSlot
return
let attestation_data_root = hash_tree_root(attestation.data)
# TODO withValue is an abomination but hard to use anything else too without
# creating an unnecessary AttestationEntry on the hot path and avoiding
# multiple lookups
pool.candidates[candidateIdx.get()].withValue(attestation_data_root, entry) do:
if not addAttestation(entry[], attestation, signature):
return
do:
if not addAttestation(
pool.candidates[candidateIdx.get()].mgetOrPut(
attestation_data_root,
AttestationEntry(
data: attestation.data,
committee_len: attestation.aggregation_bits.len())),
attestation, signature):
return
pool.addForkChoiceVotes(
attestation.data.slot, attesting_indices,
attestation.data.beacon_block_root, wallTime)
# Send notification about new attestation via callback.
if not(isNil(pool.onAttestationAdded)):
pool.onAttestationAdded(attestation)
func covers*(
pool: var AttestationPool, data: AttestationData,
bits: CommitteeValidatorsBits): bool =
## Return true iff the given attestation already is fully covered by one of
## the existing aggregates, making it redundant
## the `var` attestation pool is needed to use `withValue`, else Table becomes
## unusably inefficient
let candidateIdx = pool.candidateIdx(data.slot)
if candidateIdx.isNone:
return false
let attestation_data_root = hash_tree_root(data)
pool.candidates[candidateIdx.get()].withValue(attestation_data_root, entry):
if entry[].covers(bits):
return true
false
proc addForkChoice*(pool: var AttestationPool,
epochRef: EpochRef,
blckRef: BlockRef,
unrealized: FinalityCheckpoints,
blck: ForkyTrustedBeaconBlock,
wallTime: BeaconTime) =
## Add a verified block to the fork choice context
let state = pool.forkChoice.process_block(
pool.dag, epochRef, blckRef, unrealized, blck, wallTime)
if state.isErr:
# This indicates that the fork choice and the chain dag are out of sync -
# this is most likely the result of a bug, but we'll try to keep going -
# hopefully the fork choice will heal itself over time.
error "Couldn't add block to fork choice, bug?",
blck = shortLog(blck), err = state.error
iterator attestations*(pool: AttestationPool, slot: Opt[Slot],
committee_index: Opt[CommitteeIndex]): Attestation =
let candidateIndices =
if slot.isSome():
let candidateIdx = pool.candidateIdx(slot.get())
if candidateIdx.isSome():
candidateIdx.get() .. candidateIdx.get()
else:
1 .. 0
else:
0 ..< pool.candidates.len()
for candidateIndex in candidateIndices:
for _, entry in pool.candidates[candidateIndex]:
if committee_index.isNone() or entry.data.index == committee_index.get():
var singleAttestation = Attestation(
aggregation_bits: CommitteeValidatorsBits.init(entry.committee_len),
data: entry.data)
for index, signature in entry.singles:
singleAttestation.aggregation_bits.setBit(index)
singleAttestation.signature = signature.toValidatorSig()
yield singleAttestation
singleAttestation.aggregation_bits.clearBit(index)
for v in entry.aggregates:
yield entry.toAttestation(v)
type
AttestationCacheKey* = (Slot, uint64)
AttestationCache = Table[AttestationCacheKey, CommitteeValidatorsBits] ##\
## Cache for quick lookup during beacon block construction of attestations
## which have already been included, and therefore should be skipped.
func getAttestationCacheKey(ad: AttestationData): AttestationCacheKey =
# The committee is unique per slot and committee index which means we can use
# it as key for a participation cache - this is checked in `check_attestation`
(ad.slot, ad.index)
func add(
attCache: var AttestationCache, data: AttestationData,
aggregation_bits: CommitteeValidatorsBits) =
let key = data.getAttestationCacheKey()
attCache.withValue(key, v) do:
v[].incl(aggregation_bits)
do:
attCache[key] = aggregation_bits
func init(T: type AttestationCache, state: phase0.HashedBeaconState): T =
# Load attestations that are scheduled for being given rewards for
for i in 0..<state.data.previous_epoch_attestations.len():
result.add(
state.data.previous_epoch_attestations[i].data,
state.data.previous_epoch_attestations[i].aggregation_bits)
for i in 0..<state.data.current_epoch_attestations.len():
result.add(
state.data.current_epoch_attestations[i].data,
state.data.current_epoch_attestations[i].aggregation_bits)
func init(
T: type AttestationCache,
state: altair.HashedBeaconState | bellatrix.HashedBeaconState,
cache: var StateCache): T =
# Load attestations that are scheduled for being given rewards for
let
prev_epoch = state.data.get_previous_epoch()
cur_epoch = state.data.get_current_epoch()
template update_attestation_pool_cache(
epoch: Epoch, participation_bitmap: untyped) =
let committees_per_slot = get_committee_count_per_slot(
state.data, epoch, cache)
for committee_index in get_committee_indices(committees_per_slot):
for slot in epoch.slots():
let committee = get_beacon_committee(
state.data, slot, committee_index, cache)
var
validator_bits = CommitteeValidatorsBits.init(committee.len)
for index_in_committee, validator_index in committee:
if participation_bitmap[validator_index] != 0:
# If any flag got set, there was an attestation from this validator.
validator_bits[index_in_committee] = true
result[(slot, committee_index.uint64)] = validator_bits
# This treats all types of rewards as equivalent, which isn't ideal
update_attestation_pool_cache(
prev_epoch, state.data.previous_epoch_participation)
update_attestation_pool_cache(
cur_epoch, state.data.current_epoch_participation)
func score(
attCache: var AttestationCache, data: AttestationData,
aggregation_bits: CommitteeValidatorsBits): int =
# The score of an attestation is loosely based on how many new votes it brings
# to the state - a more accurate score function would also look at inclusion
# distance and effective balance.
# TODO cache not var, but `withValue` requires it
let
key = data.getAttestationCacheKey()
bitsScore = aggregation_bits.countOnes()
attCache.withValue(key, value):
doAssert aggregation_bits.len() == value[].len(),
"check_attestation ensures committee length"
# How many votes were in the attestation minues the votes that are the same
return bitsScore - aggregation_bits.countOverlap(value[])
# Not found in cache - fresh vote meaning all attestations count
bitsScore
proc getAttestationsForBlock*(pool: var AttestationPool,
state: ForkyHashedBeaconState,
cache: var StateCache): seq[Attestation] =
## Retrieve attestations that may be added to a new block at the slot of the
## given state
## https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.1/specs/phase0/validator.md#attestations
let newBlockSlot = state.data.slot.uint64
if newBlockSlot < MIN_ATTESTATION_INCLUSION_DELAY:
return # Too close to genesis
let
# Attestations produced in a particular slot are added to the block
# at the slot where at least MIN_ATTESTATION_INCLUSION_DELAY have passed
maxAttestationSlot = newBlockSlot - MIN_ATTESTATION_INCLUSION_DELAY
startPackingTick = Moment.now()
var
candidates: seq[tuple[
score: int, slot: Slot, entry: ptr AttestationEntry, validation: int]]
attCache =
when state is phase0.HashedBeaconState:
AttestationCache.init(state)
elif state is altair.HashedBeaconState or state is bellatrix.HashedBeaconState:
AttestationCache.init(state, cache)
else:
static: doAssert false
for i in 0..<ATTESTATION_LOOKBACK:
if i > maxAttestationSlot: # Around genesis..
break
let
slot = Slot(maxAttestationSlot - i)
candidateIdx = pool.candidateIdx(slot)
if candidateIdx.isNone():
# Passed the collection horizon - shouldn't happen because it's based on
# ATTESTATION_LOOKBACK
break
for _, entry in pool.candidates[candidateIdx.get()].mpairs():
entry.updateAggregates()
for j in 0..<entry.aggregates.len():
let
attestation = entry.toAttestation(entry.aggregates[j])
# Attestations are checked based on the state that we're adding the
# attestation to - there might have been a fork between when we first
# saw the attestation and the time that we added it
if check_attestation(state.data, attestation, {}, cache).isErr():
continue
let score = attCache.score(
entry.data, entry.aggregates[j].aggregation_bits)
if score == 0:
# 0 score means the attestation would not bring any votes - discard
# it early
# Note; this must be done _after_ `check_attestation` as it relies on
# the committee to match the state that was used to build the cache
continue
# Careful, must not update the attestation table for the pointer to
# remain valid
candidates.add((score, slot, addr entry, j))
# Using a greedy algorithm, select as many attestations as possible that will
# fit in the block.
#
# For each round, we'll look for the best attestation and add it to the result
# then re-score the other candidates.
#
# A possible improvement here would be to use a maximum cover algorithm.
var
prevEpoch = state.data.get_previous_epoch()
prevEpochSpace =
when state is altair.HashedBeaconState or state is bellatrix.HashedBeaconState:
MAX_ATTESTATIONS
elif state is phase0.HashedBeaconState:
state.data.previous_epoch_attestations.maxLen -
state.data.previous_epoch_attestations.len()
else:
raiseAssert "invalid HashedBeaconState fork"
var res: seq[Attestation]
let totalCandidates = candidates.len()
while candidates.len > 0 and res.lenu64() < MAX_ATTESTATIONS:
block:
# Find the candidate with the highest score - slot is used as a
# tie-breaker so that more recent attestations are added first
let
candidate =
# Fast path for when all remaining candidates fit
if candidates.lenu64 < MAX_ATTESTATIONS: candidates.len - 1
else: maxIndex(candidates)
# TODO slot not used; replace with _ when
# https://github.com/nim-lang/Nim/issues/15972 and
# https://github.com/nim-lang/Nim/issues/16217 are
# fixed in Status's Nim.
(_, slot, entry, j) = candidates[candidate]
candidates.del(candidate) # careful, `del` reorders candidates
if entry[].data.target.epoch == prevEpoch:
if prevEpochSpace < 1:
continue # No need to rescore since we didn't add the attestation
prevEpochSpace -= 1
res.add(entry[].toAttestation(entry[].aggregates[j]))
# Update cache so that the new votes are taken into account when updating
# the score below
attCache.add(entry[].data, entry[].aggregates[j].aggregation_bits)
block:
# Because we added some votes, it's quite possible that some candidates
# are no longer interesting - update the scores of the existing candidates
for it in candidates.mitems():
it.score = attCache.score(
it.entry[].data,
it.entry[].aggregates[it.validation].aggregation_bits)
candidates.keepItIf:
# Only keep candidates that might add coverage
it.score > 0
let
packingDur = Moment.now() - startPackingTick
debug "Packed attestations for block",
newBlockSlot, packingDur, totalCandidates, attestations = res.len()
attestation_pool_block_attestation_packing_time.set(
packingDur.toFloatSeconds())
res
proc getAttestationsForBlock*(pool: var AttestationPool,
state: ForkedHashedBeaconState,
cache: var StateCache): seq[Attestation] =
withState(state):
pool.getAttestationsForBlock(state, cache)
func bestValidation(aggregates: openArray[Validation]): (int, int) =
# Look for best validation based on number of votes in the aggregate
doAssert aggregates.len() > 0,
"updateAggregates should have created at least one aggregate"
var
bestIndex = 0
best = aggregates[bestIndex].aggregation_bits.countOnes()
for i in 1..<aggregates.len():
let count = aggregates[i].aggregation_bits.countOnes()
if count > best:
best = count
bestIndex = i
(bestIndex, best)
func getAggregatedAttestation*(pool: var AttestationPool,
slot: Slot,
attestation_data_root: Eth2Digest): Opt[Attestation] =
let
candidateIdx = pool.candidateIdx(slot)
if candidateIdx.isNone:
return Opt.none(Attestation)
pool.candidates[candidateIdx.get].withValue(attestation_data_root, entry):
entry[].updateAggregates()
let (bestIndex, _) = bestValidation(entry[].aggregates)
# Found the right hash, no need to look further
return Opt.some(entry[].toAttestation(entry[].aggregates[bestIndex]))
Opt.none(Attestation)
func getAggregatedAttestation*(pool: var AttestationPool,
slot: Slot,
index: CommitteeIndex): Opt[Attestation] =
## Select the attestation that has the most votes going for it in the given
## slot/index
## https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.1/specs/phase0/validator.md#construct-aggregate
let
candidateIdx = pool.candidateIdx(slot)
if candidateIdx.isNone:
return Opt.none(Attestation)
var res: Opt[Attestation]
for _, entry in pool.candidates[candidateIdx.get].mpairs():
doAssert entry.data.slot == slot
if index != entry.data.index:
continue
entry.updateAggregates()
let (bestIndex, best) = bestValidation(entry.aggregates)
if res.isNone() or best > res.get().aggregation_bits.countOnes():
res = Opt.some(entry.toAttestation(entry.aggregates[bestIndex]))
res
proc selectOptimisticHead*(
pool: var AttestationPool, wallTime: BeaconTime): Opt[BlockRef] =
## Trigger fork choice and returns the new head block.
## Can return `nil`
# TODO rename this to get_optimistic_head
let newHead = pool.forkChoice.get_head(pool.dag, wallTime)
if newHead.isErr:
error "Couldn't select head", err = newHead.error
err()
else:
let ret = pool.dag.getBlockRef(newHead.get())
if ret.isErr():
# This should normally not happen, but if the chain dag and fork choice
# get out of sync, we'll need to try to download the selected head - in
# the meantime, return nil to indicate that no new head was chosen
warn "Fork choice selected unknown head, trying to sync", root = newHead.get()
pool.quarantine[].addMissing(newHead.get())
ret
proc prune*(pool: var AttestationPool) =
if (let v = pool.forkChoice.prune(); v.isErr):
# If pruning fails, it's likely the result of a bug - this shouldn't happen
# but we'll keep running hoping that the fork chocie will recover eventually
error "Couldn't prune fork choice, bug?", err = v.error()
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